September weather forecast and climate
Key Largo, FL

A clear seascape and cloudy evening sky in Key Largo, Florida
A clear seascape and cloudy evening sky in Key Largo, Florida

Weather in September

September, the first month of the autumn, in Key Largo, is also a moderately hot month, with average temperature fluctuating between 81.7°F (27.6°C) and 84.6°F (29.2°C).

Temperature

In Key Largo, the average high-temperature is almost the same as in August - a still warm 84.6°F (29.2°C). In Key Largo, in September, the average low-temperature is 81.7°F (27.6°C).

Heat index

In September, the average heat index is appraised at a hot 93.2°F (34°C). Take extra precautions, as heat cramps and heat exhaustion are possible. Sustained activity may result in heatstroke.
Take into consideration that the heat index values are calculated for shade and light wind conditions. With the exposure to direct sunlight, the heat index may be increased by up to 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'felt air temperature', 'real feel', 'apparent temperature', or 'feels like', is a measure of how hot it feels when the actual air humidity is factored in. This effect is subjective, depending on the activity and individual's heat perception influenced by various reasons (metabolic differences, wind, clothing). Be aware that direct exposure to sunlight increases heat impact, and may raise the heat index additionally, by up to 15 Fahrenheit (8 Celsius) degrees. Heat index values are especially crucial for babies and toddlers. Young children are generally more endangered than adults, as they usually less sweat. And also, due to larger skin surface relative to their small bodies and higher heat production as a result of their activity.

Humidity

In September, the average relative humidity in Key Largo is 74%.

Rainfall

In September, in Key Largo, the rain falls for 22.9 days. Throughout September, 4.25" (108mm) of precipitation is accumulated. In Key Largo, Florida, during the entire year, the rain falls for 190.1 days and collects up to 27.05" (687mm) of precipitation.

Ocean temperature

In Key Largo, the average seawater temperature is 85.6°F (29.8°C).
Note: Water temperature between 77°F (25°C) and 84.2°F (29°C) is regarded as very warm and enjoyable by all. With these temperatures, water activities are pleasurable, without feeling uncomfortable for prolonged periods.

Daylight

In Key Largo, Florida, the average length of the day in September is 12.3h.

Sunshine

The average sunshine in Key Largo is 9h.

UV index

Months with the highest UV index are April through October, with an average maximum UV index of 7. A UV Index estimate of 6 to 7 represents a high threat to health from the exposure to the Sun's UV rays for ordinary individuals.
Note: In September, the average maximum UV index of 7 translate into the following recommendations:
Take precautions against overexposure. Fair-skinned people may get burned in less than 20 minutes. Seek shade and minimize exposure to direct Sun in a period between 10 a.m. and 4 p.m. when UV radiation is most intense; keep in mind that shade structures like parasols or canopies do not provide perfect sun protection. A wide-brim hat offers excellent sun protection for eyes, ears, face, and neck. Sunglasses with UVA and UVB protection significantly reduce eye damage from sun exposure. Tightly woven, loose-fitting clothes provide additional protection from the Sun. Caution! The reflection of sand and water significantly increases the intensity of the Sun's UV radiation.
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FAQ

What is the temperature in September in Key Largo?

In September, the average high-temperature is 84.6°F (29.2°C), and the average low-temperature is 81.7°F (27.6°C). The average heat index (a.k.a. 'apparent temperature', 'felt air temperature'), that represents influence of the relative humidity to air temperaure, in September is estimated at 93.2°F (34°C).

What is the average humidity in September in Key Largo?

In September, the average relative humidity in Key Largo is 74%.

How many days does it rain in September in Key Largo?

In September, in Key Largo, the rain falls for 22.9 days. Throughout September, 4.25" (108mm) of precipitation is accumulated.

What is the ocean temperature in September in Key Largo?

In Key Largo, the average seawater temperature in September is 85.6°F (29.8°C). For any water activity, surface water temperatures between 77°F (25°C) and 84.2°F (29°C) are considered as excellent and extremely pleasant for lengthened periods.

How many hours of daylight does Key Largo have in September?

In Key Largo, Florida, the average length of the day in September is 12.3h.

How many hours of sunshine does Key Largo have in September?

In Key Largo, Florida, the average sunshine in September is 9h.

When is the highest UV index in Key Largo?

Months with the highest UV index in Key Largo are April through October, with an average maximum UV index of 7.

What is the UV index reading in September in Key Largo?

In Key Largo, Florida, the average daily maximum UV index in September is 7. A UV Index of 6 to 7 symbolizes a high hazard to health from the exposure to the Sun's UV rays.

Average temperature in September
Key Largo, FL

Average temperature in September - Key Largo, FL
  • Average high temperature in September: 84.6°F

The warmest month (with the highest average high temperature) is August (85.5°F).
The month with the lowest average high temperature is January (72.7°F).

  • Average low temperature in September: 81.7°F

The month with the highest average low temperature is August (82.9°F).
The coldest month (with the lowest average low temperature) is January (66.9°F).

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Average pressure in September
Key Largo, FL

Average pressure in September - Key Largo, FL
  • Average pressure in September: 29.94"

The month with the highest atmospheric pressure is January (30.1").
Months with the lowest atmospheric pressure are September and October (29.94").

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Average wind speed in September
Key Largo, FL

Average wind speed in September - Key Largo, FL
  • Average wind speed in September: 9.4mph

The windiest month (with the highest average wind speed) is January (12.9mph).
The calmest month (with the lowest average wind speed) is July (8.9mph).

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Average humidity in September
Key Largo, FL

Average humidity in September - Key Largo, FL
  • Average humidity in September: 74%

Months with the highest relative humidity are February, June and December (76%).
The month with the lowest relative humidity is March (73%).

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Average rainfall in September
Key Largo, FL

Average rainfall in September - Key Largo, FL
  • Average rainfall in September: 4.25"

The wettest month (with the highest rainfall) is August (4.33").
The driest month (with the least rainfall) is March (0.59").

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Average rainfall days in September
Key Largo, FL

Average rainfall days in September - Key Largo, FL
  • Average rainfall days in September: 22.9 days

The month with the highest number of rainy days is September (22.9 days).
The month with the least rainy days is February (9.7 days).

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Average sea temperature in September
Key Largo, FL

Average sea temperature in September - Key Largo, FL
  • Average sea temperature in September: 85.5°F

The best month for swimming (with the highest average sea temperature) is August (86.5°F).
The coldest month (with the lowest average sea temperature) is February (74°F).

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Average daylight in September /
Average sunshine in September
Key Largo, FL

Average daylight in September / Average sunshine in September - Key Largo, FL
  • Average daylight in September: 12.3h

The month with the longest days is June (Average daylight: 13.7h).
The month with the shortest days is December (Average daylight: 10.6h).

  • Average sunshine in September: 9h

The month with the most sunshine is July (Average sunshine: 11h).
The month with the least sunshine is December (Average sunshine: 6.4h).

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Average sunshine days in September
Key Largo, FL

Average sunshine days in September - Key Largo, FL
  • Average sunshine days in September: 5.2 days

The month with the most sunshine days is January (17.3 days).
The month with the least sunshine days is September (5.2 days).

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Average UV index in September
Key Largo, FL

Average UV index in September - Key Largo, FL
  • Average UV index in September: 7

Months with the highest UV index are April, May, June, July, August, September and October (UV index 7).
The month with the lowest UV index is January (UV index 5).

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Average cloud cover in September
Key Largo, FL

Average cloud cover in September - Key Largo, FL
  • Average cloud cover in September: 30

The month with the most cloud cover is October (Cloud cover 35).
The month with the least cloud cover is April (Cloud cover 26).

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Average visibility in September
Key Largo, FL

Average visibility in September - Key Largo, FL
  • Average visibility in September: 6mi

Months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
Months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).

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